package yukicoder;

import java.util.Scanner;

public class N208 {
	public static void main(String[] args){
		Scanner sc = new Scanner(System.in);
		int x = sc.nextInt();
		int y = sc.nextInt();
		int hx = sc.nextInt();
		int hy = sc.nextInt();
		int ななめ = Math.min(Math.abs(x), Math.abs(y));
		int step;
		if(hx == hy && Math.abs(hx) <= ななめ){
			step = 2;
		}else if(Math.abs(hx) > ななめ || Math.abs(hy) > ななめ){
			step = 1;
		}else{
			step = 0;
		}
		System.out.println(Math.max(x, y) + step);
		
	}
}